Function requestSignature

requestSignature(
    requestId: string,
    timestamp: string | Date,
    signKey: string,
    operations?: SignedOperation[],
): string
Compute the user/requestSignature value.

NAV specifies the signature as
```
SHA3-512( requestId || yyyyMMddHHmmss(timestamp) || signKey || hash(op1) || hash(op2) ... )
```
where the per-operation hashes are only present for manageInvoice and manageAnnulment requests and must be concatenated in ascending index order. The timestamp must be the request header timestamp truncated to whole seconds and rendered in UTC without separators.
Parameters
- requestId: string
  the header/requestId of the same request
- timestamp: string | Date
  the header/timestamp of the same request
- signKey: string
  the technical user's signature key (aláírókulcs)
- operations: SignedOperation[] = []
  invoice/annulment operations of the batch, if any
Returns string
- Defined in packages/core/src/crypto/signature.ts:46